1. Field of the Invention
The present invention relates generally to medical tables for medical procedures, and, in particular, relates to tables that are used for vascular and interventional medical procedures, and, in greater particularity, relates to tables having an iso-axis.
2. Description of the Prior Art
Fluoroscopic imaging devices are an important tool for minimally invasive surgical and interventional procedures because they provide a real-time x-ray view of internal anatomical features whether of tissues, bones, or organs. The x-ray images are displayed on a video monitor(s) that is located so as to be viewable by the surgeon or interventionalist during the patient procedure. Mobile fluoroscopic imaging devices (mobile fluoroscopes) are equipped with an x-ray control system; an x-ray image video monitor display stand; and an x-ray source and image receptor which are mounted to a semicircular gantry designed to permit either manual or motorized movement of the gantry in order to position the x-ray source and image receptor around and about the subject patient anatomy. Manual or motorized positioning of the x-ray source and image receptor gantry, relative to the subject anatomy, includes vertical height adjustment, horizontal movement in the longitudinal and lateral directions, orbital rotation around the patient, and cranial-caudal rotation (along the head-to-toe axis). Mobile fluoroscopes are used with a mobile patient table with a cantilevered and radiolucent tabletop that serves to support the patient and allow the x-ray source and image receptor free movement around and about the patient.
During surgical or interventional procedure involving fluoroscopy, an iso-center is defined as the orbital center, or the point about which the x-ray source and image receptor rotate. An object of anatomical interest positioned at the iso-center will remain within the field of view as the imaging system is rotated and re-positioned about the patient. It is thus very important and beneficial to be able to position the anatomical region of interest at such a point of iso-center during the procedure. In some procedures the tabletop must be tilted to provide better access to the patient anatomy. If the anatomical region of interest is placed on the imaging iso-center and the table can provide iso-centric rotation (tilt), the imaging system and/or the table can be rotated without having the region of interest move outside the imaging area.
The fluoroscope gantry or the patient tabletop supporting the patient for such procedures thus must be moved if additional anatomical areas are to be observed. Many of the tables used for these procedures have tabletops that can be moved with many degrees of freedom. Existing tables typically have a point of tabletop tilt rotation that is located under the tabletop; thus as the tabletop is tilted the tabletop is displaced left or right as it swings about an arc with a center of rotation located under the table top and patient. Thus, during fluoroscopic imaging, if the table top is tilted to the left or right a region of interest within the anatomy of a patient will appear to move laterally across the field of view of the imaging system. If the center or axis of rotation could be displaced from a location under the table to a point above it then the table axis of rotation could be placed in a location that would be of benefit relative to the position of key parts of the human anatomy, the spine for example, as well as simultaneously coincident with the axis of rotation of the imaging system. If the table axis of rotation is placed on iso-center along with the region of interest (a section of the spine) then table rotation can be accomplished without causing the region of interest to drift or move out of the field of view.
There are some table designs that utilize complex linkages and mechanisms to create an approximation of an axis of rotation that is located above the table top. In such designs the point of rotation is not fixed though it does exist above the table top and within a patient's anatomy.
The manufacturing of these tables thus should minimize complex mechanical devices providing these many degrees of freedom to reduce the cost of these tables.
Examples of tables are shown in several patents and patent application publications. U.S. Patent Application 2003/0145383 discloses a lateral tilting device using four legs driven by a motorized screw. The top of the legs are attached to the tabletop and the bottom to the support column. U.S. Patent Application 2004/0172758 discloses a table having longitudinal tilt with the ability to provide iso-center tracking. The iso-center being a point at which radiation is provided to the patient by the radiating machine. U.S. Patent Application 2005/0015878 discloses a lateral and longitudinal tilting device. A frame is mounted to a support column. The frame is pivoted on orthogonal axes having two actuators driving the respective frame. The axes of rotation are thus below the tabletop. U.S. Pat. No. 6,094,760 discloses a table having a lateral tilting device. The tabletop has a pair of circular tracks that travel upon rolls thereunder. A driving means is attached to an axle under the tabletop. U.S. Pat. No. 6,681,423 discloses a table with lateral tilt using four legs between a top and bottom frame. A pair of actuators controls the movement of the top frame. U.S. Pat. No. 7,000,271 discloses a C-arm x-ray machine providing x-rays to an iso-center point.
Accordingly, there is a need for an imaging table having an iso-roll axis above the tabletop and located on or substantially close to the iso-center of the imaging system.